As far as investigated, due the the bitcoin network will grow its diff levels if the blocks are generated too fast (faster than 1 blk per 10 mins), if so, the will that be necessary to buy ASIC to mine it yourself? What do you guys think?

It's definitely possible. Since bitcoins are limited resource, but the prerequisites is that bitcoin are being accepted by most of the merchants and circulate in everyone's daily expenses.

Bitcoin has to be accepted by many merchants in order to set up it's currency role as well as stability. We'v been seeing people buying and selling for bitcoins only for investment, if this is not minimized, another ponzi.