There is no potential either unlimited or with a certain cap, it only devalue the coin.

Altcoins are always working as testing phase for bitcoins. These mentioned coins could be consider for what would have happened with bitcoins with unlimited supply. (Here we cannot be staying calm without remembering Mr.Satoshi and his fore-vision on how a new momentary system should be). I believe there will be more time before we can make any conclusion on the future of these coins. But as of now I am not seeing any demand for them to surge up again.

Almost 90% of cyptocoins users cannot deny that they are adopting cryptocurrencies with speculations. But with uncaped coins, we cannot be sure how the future will be. In other words there would be no minimum guarantee too. I too doubt about their sustainability.

Unlimited supply is one thing that will cause price to drop and it does not even work in the real world not to talk of the crypto world and that is why government does not just go ahead and start printing money as they want because of the issue of supply and even in elementary economics, one characteristics of money is for it to be relatively scarce if its going to be worthy which unlimited supply negates and that is a fundamental flaw from the beginning of the project.

I think you are confusing three notions.  One is "unlimited" supply, the other is "infinite supply" and the third is "arbitrary supply".  You are arguing against "infinite supply" and "arbitrary supply".  Obviously, nothing with infinite supply can have any other market value than 0.  If the amount of coins in circulation are INFINITE, then of course, they are worth nothing.

Arbitrary supply means that there are entities which can create, *at any moment*, *any finite amount of extra supply*.  Although arbitrary supply means that at any moment in time, there's a finite number of coins in circulation, the amount of coins at the next moment is simply UNCERTAIN.  It could be N + n.  It could be N + 500 n.  The entities capable of supplying arbitrary amounts of coins, have access to arbitrary amounts of seigniorage, and can hence give themselves just ANY fraction of the market cap.  If there are 1000 coins in circulation today, they could decide suddenly that tomorrow, there are 1 million coins in circulation.

Although arbitrary supply could mean a finite market price for those entities NOT capable of creating coins, if they *really need it*, but they will try to have their minimum demand for it, so the market price of it will be whatever is the inelastic demand for it.  For instance, if I were a dictator, issuing coins at will, and making a law that any person on the street NOT in provable possession of k coins, will be shot on the spot without any further form of process, then the inelastic demand for my coins will be m x k, where m is the number of people not wanting to get shot.  I could print 100 times more of these coins, some smart dealers will buy them at some price from me, to sell a small part of it way way more expensively to the poor people needing these coins.  There WILL be a finite market price for these coins, even if I can emit an arbitrary supply of it.
BTW, this is more or less what a fiat system does, and the k coins are your due taxes which create an inelastic demand for fiat money.   But without the use of violence to impose an inelastic demand for them, usually they are worthless.

However, "unlimited supply" doesn't mean "infinite supply" nor "arbitrary supply".  It simply means that at a moment in time, the supply is N coins, and at a later moment in time, the supply is N + n coins.  Both these numbers are finite and KNOWN.

Now, whether that suite diverges AT INFINITY or not doesn't matter.  ANY emission scheme has a finite amount of emitted coins before the earth gets burned by the sun turning in a red giant 5 billion years from now.  

A coin emission that emits 5% of its existing stash every year will still have a finite and limited amount of coins in circulation 5 billion years from now.  The only difference between a coin with "unlimited supply" and a coin with "limited supply" is at time = infinity, when the coin (earth, humanity....) will not exist any more.

With a given emission scheme of which one can deterministically predict the amount of coins in circulation AT ANY FUTURE MOMENT, there is no difference between a coin with "finite supply" and a coin with "unlimited supply".  Take the coin with "unlimited supply", calculate how many coins there will be 5 billion years from now, and that is a finite number.  Well, what's the difference between such a coin, and a coin that will emit the same number of coins over 100 years, and then not emit anything any more ?  It simply took LONGER for the "unlimited supply" coin to get there, than the "limited supply coin" !  So it seems that the inflation of the "limited supply coin" was worse than the "unlimited supply coin".

Bitcoin, at this moment, still has several percent inflation.  It is worse in that respect than an unlimited supply coin with an emission rate of 1% inflation continuously.

I took the earth's end as ultimate limit, but of course, all monetary assets break down at a certain point, undergo hyperinflation, and are left for worth zero.  This will happen to every fiat currency (there is not one single fiat currency that has more than, say, 1000 years as far as I know) ; it will happen to every crypto currency, yes, to bitcoin too.  In 50 years, 150 years, or 500 years or 5000 years, bitcoin will be worthless, and forgotten apart from some historical fact.

This is the time scale over which an emission scheme should be looked at, and every scheme will have issued a finite amount of coins when the coin hyperinflates and becomes essentially worthless.  So there's no difference.

Monetary assets don't last for eternity, even though the monetary belief in it takes that for granted.  But the real idea is to get rid of it (in the hands of "greater fools") like a hot potato before it hyperinflates.  In the mean time, you can use it as a store of value, currency or speculative asset.