NEW Counter-Strike? ... or keep updating Global Offensive?

Starting off with your question, if they released source 2 and moved CS:GO over to it the game will be revived and be in a much better state than it is now. Regarding the "investing more money in VAC" thing, they added the whole VACnet thing which is supposed to be the upgraded version of VAC as far as I know. The processing power they require to run this (and even more since their upgrading it) is a lot, so spending more money on VAC only for a new CS is pointless when they can just continue upgrading and improving the current one.