Yep, from 1993 to 2003 the typical Tour player added something like 28 yards to his driving distance. The rest of that long-term trend chart looks like basically an equilibrium situation obtained in the 80's and early 90's and a new equilibrium has developed from about 2005 onward.
Of course there is still some driving distance potential unrealized seeing as how not every Tour player hits driver on every hole. So one alternative explanation that no doubt forms at least a small part of that pattern is the possibility that current driving distance reflect not an absolutely 'hit it as far as I can every time" limit but rather it's a sweet spot in the risk-vs-reward calculation, conditional on the course setups on which they play.
My theory for quite some time has been that there's a slow, inexorable increase in distance capability as each generation of players becomes stronger and develops better technique. But that's a slow process and would take decades to cause, say, a 10-yard increase in median driving distance. The USGA was derelict in the golf ball regulation duties for basically the decade of the 1990's. That caused a one-time almost step function increase of around 25-30 yards on top of the natural slow evolution that existed before and since that period. To a certain extent the changeover in drivers contributed but I think the ProV1 effect swamped the Titanium effect, so to speak.