I agree, and would add that it seems likely that spheres will also be less effective as decks begin to run more land and mana producers. Decks like MServant and Bomberman will have healthy manabases, and will probably run drains in addition to their other counter/disruption  suite. 

As many other people have already noted on TMD, a large percentage of the deck's making it to the final table in recent month's have contained the same basic shell. If a player were running blue one usually could expect to see 4 Gush, 4 Brainstorm, usually 3-4 Merchant Scroll, and sometimes 4 Ponder, as well as the perfunctory 4 FoW.  My question, and the reason for this post, is to discuss whether the  6-1 Banned & Restricted changes will cause a precipitous increase in the number of Mana Drain's being played.

As I see it, the restriction of gush (again) on top of Brainstorm, Scroll, and Ponder will work to slow the format down slightly. The best draw engine--probably ever--is gone, which works to the advantage of deck's like Control Slaver which was just to slow to compete with the Gush/Bond engine. Will decks like Slaver have a chance again--perhaps splashing Servant's--or will Blue control go in an entirely new direction? In any of these possible scenarios will Mana Drain make the comback I foresee, thus preserving Blue's spot as the default go-to-color, or will the absence of so many other blue staples keep people from flocking to drain?