I don't think "seasonal" pricing is imminent--just something they're thinking about. The new ticket system is already really complex, so I'd be surprised to see it get more complex any time soon, and I certainly wouldn't worry about it....
While part of the motivation of seasonal pricing might be to maximize profits, it seems to me a goal would be to distribute crowds more evenly. With such a large proportion of crowds being AP holders, Disney can definitely predict, and maybe even distribute, a lot of the crowds using blockout dates. (Notice how crowded the days before a blockout period are!)
Whereas at best, IMO price adjustments for "peak periods" would be an unpredictable way to shift crowds. I don't personally think the seasonal pricing would affect the crowds even close to as much as AP blockouts. But it's not impossible that seasonal pricing could make previously uncrowded times a zoo. If nothing else, Disney might hesitate because it's a really sweeping change that could have very unpredictable results and limited benefits, with potential guest backlash.
The two weeks around Christmas DO seem to be busy whatever Disney does. But if Al is right, then Disney has considered separate-ticket Christmas parties to increase revenue in the holiday period, while providing periods of reduced crowds at a premium price. So anyway, seasonal pricing is certainly not the only tool Disney has for crowd control OR for maximizing profits. Will be interesting to see what they do!