We should never underestimate the potential of Zenit. There just about to move into a brand new almost 70000 stadium and will have champion league football every year almost guaranteed.
I don't think he will go to Russia, Zenit might qualify for the Champions League every year, but the standard of the domestic competition is lower than the Premiership and he may not get that much more money.
Zenit will not automatically qualify for the Champions League every year! Where is this assumption coming from anyway? I reckon Russia's association ranking rises and falls (between 6th and 7th position) so they either get 2 or 3 CL qualifying spots. You have to remember all the competition as well, plus factoring in the Anzhi effect. It wouldn't be too hard to see Zenit finishing behind CSKA Moscow, Spartak and Anzhi in the coming years..... and that means no CL for Zenit.
EDIT: Russia only has TWO Champions League spots again next year since their association ranking has fallen.
http://en.wikipedia.org/wiki/2013–14_UEFA_Champions_League#Association_team_allocation