Nothing within our current technology or knowledge of the plates (we have a pretty minimal grasp on what processes drive these plates and more of a bunch of assumptions that kinda seem right anyway). This isn't to say it isn't possible and we can't speculate a little on what could do it...
The biggest issue to get around isn't just the size and magnitude of the energy that these moving plates have, but also the timeline they operate on. They literally move just inches a year...over a geological time scale, it's actually kinda quick, but to us humans this change is so subtle that we can't perceive the motion. As your question properly states : "something in a few million years"...and therein lies the problem. Whatever is changing the motion also has to act over this multi-million year timeframe, or the changes would be abrupt enough that our world on the surface would be destroyed by massive earthquakes beyond what we've ever seen. I guess the first question presents itself as 'who alive now would possibly care what state the world is in 1 million years from now, and more-so why would they invest time and energy now to change something 1 million years from now?
The other issue here is the plates interact. To move one plate in a different direction would either need to push another plate in a different direction as well, or require two plates to push further together. Altering a single plates motion might create entire mountain ranges elsewhere (over the million of years time scale of course).
Unfortunately I can't imagine much for means to do this. Id suggest to you that a type II civilization on the Kardashev scale would be the minimum requirement to undertake such a feat.
(complete side note, but I'm getting a laugh from spell check changing Kardashev to Haberdasher)