Good question,
Mainframes are still here, and in my opinion, will be here for a long time to come. Are we moving back to them? I'd say absolutely not. They will be around, but the growth of technology today, increases the demand that people put on these systems, and the newer more efficient and "feature rich" and "user friendly" environments will always prevail to the consumer and corporate markets alike.
Mainframe systems still play an important role in big business today, they have an important role, and one which is very difficult and expensive to run away from. Comapanies have invested billions, even trillions of dollars over the last 30 years in this technoloigy, and in many cases, still searching for their ROI, and will for many years to come. Meanwhile, Microsoft or Unix Based PC's, handheld devices, wireless communications, cellular technology, etc.. will continue to boom, techynology will get smaller, and more powerful, and more and more people will come to rely on them. Heck even my 95 year old grandmother surfs the web believe it or not. And with crippling arthritis to boot!
So no, IMHO we are not going back to mainframes, simply maintaining them, keeping them alive and profitable, and one day far in the future, retiring them or trading them in like we did the Commodore 64 for a newer, more powerful, more efficient, more friendly, less expensive technology.
Dave