I agree with Dan, I think it is fair to say Gerrard has done well but he has benefitted from some decent circumstances (no pressure for 2 years, Celtics incompetence following Rodgers leaving).
I think Gerrard will stay at Rangers for at least another year too. He will want a crack at the champions league, although they still do have to qualify).
A mid level prem job would be a massive risk to his aspirations of being Liverpool manager too. I think in that respect multiple titles with Rangers would be better. Especially as Celtic will not be this poor next year.
As for this season, I hope Gerrard goes the season unbeaten and scratches Celtic's name out of the record books for most points (big ask!)