OP: Most of your arguments - however valid - actually work in Bitcoin's favour.
First of all, whether Bitcoin is or isn't, or even will be "mainstream" is irrelevant. You need to look at the cryptocurrency economy as a whole and that most definitely IS going mainstream. There will probably be several actual networks that go "mainstream" because there's a need for them to support different roles as in the fiat economy where you have some forms of money that serve as a store of value and "safe haven", others which provide day to day liquidity etc.
So whether it's Bitcoin or something else doesn't matter. It's Bitcoin at the moment so if you want to "ride" this train to its destination you need to be in Bitcoin right now.
without regulation is when there's a real problem. Illegal drug trafficking sites such as Silk Road made millions off people buying drugs through Bitcoin. There needs/will be regulation of a cryptocurrency in the future.
If you're using this as your criteria, then Bitcoin most definitely IS going mainstream. The last few months have seen nothing but new regulations emerging over cryptocurrencies all over the world. Did you watch the recent 2-day New York hearing ? This is just a non-argument. Governments all over the workd have been ruling on Bitcoin regulation and clarifying things such as Value added tax status such as in the UK last week.
price fluctuations, high transaction times, transaction malleability, possibility of a 51% attack, and very high energy output to mine
I think you mis-understand what malleability actually is. It is DESIGNED into the Bitcoin protocol to make the transactions more independent of their originating application. This feature is what will allow the next tier of network applications to evolve and has nothing to do with hacking. The issue with MT Gox was that they got conned into doing double withdrawals by their customers - a bit like me sending someone $1000 from my bank account (which takes 3 days to arrive) and then someone else in the meantime finding a way to get me to send another $1000 to them.
Malliability is here to stay - there is no intention of designing it out of the Bitcoin protocol and it's simply up to clients to wait for at least 1 confirmation before recognising any funds. No problem.
As for your other points, I can't be bothered addressing them - thay are FUD and have been well addressed all over these forums.
in the future, a new cryptocurrency without all the flaws of Bitcoin will emerge, and WILL become mainstream which Bitcoin hasn't
LoL ! Have you been living on the moon for the last 3 months ? The number of Alt currencies which have emerged now numbers in the hundreds - many of them surpassing Bitcoin's specifications in all kinds of ways. Yet they haven't even made a dent in Bitcoin's status as the most established cryptocurrency network. On the contrary, they've actually enhanced it in the following ways:
[1] - by providing liquidity to the market as a proxy for Bitcoin. Make no mistake. They only reason people trade alts is to make Bitcoin gains, otherwise why would their value all be measured in BTC ?
[2] - even many of the 2nd generation protocols emerging which are being heralded as "the future" run on top of the Bitcoin network
[3] - while alt coins continue to evolve, that commercial infrastructure that is being buit - such as payment gateways, POS hardware, cryptocurrency derivative and hedging products, security services - all UNIQUELY support Bitcoin. What this means is that even though new and emerging currencies may be more practical for say-to-day or specialised uses, the value they gain is always going to be dumped into Bitcoin ultimately as long as no "show stoppers" emerge in the Bitcoin protocol (and malliability definitely IS'NT one as I outlined above)
I'll just say one last thing about your posting etiquet:
many of you are too naive, or too stupid to understand the nature of Bitcoin
Just giving you all naive suckers a heads up
Whether you think people on these forums are naive or not, you've exposed a cartoon level of understanding about the cryptocurrency economy and the Bitcoin protocol in particular and are in no position to call them "naive" or "suckers". You're lucky you got any considered replies at all with such unmitigated arrogance which I'm getting sick of on these threads and is why I made this post.
I don't really give a monkey's whether Bitcoin goes mainstream or not ultimately, for reason I stated in my first point, but one thing that could do with staying out of the mainstream is baseless inflammatory chaff like this original post.