The fetchlands were overdue for a reprint. I don't follow it any more, but for a while I read Maro's blog. IIRC, he said they didn't anticipate the astronomical price jump, and since sets are designed a year or two before they're printed, they couldn't get them out as soon as they'd have liked. It's not healthy for the game when new players are priced out of it.
Anything not on the reserve list is fair game for a reprint, and as a player that's a risk you take when acquiring or holding onto expensive cards. Despite that, WotC is mindful of the secondary market and is careful about reprints. They have to be. Even though they don't profit from it directly, the secondary market needs to thrive in order for the game to stay alive. People aren't going to want to buy new product without some confidence that the cards will maintain value long-term. WotC has to perform a delicate balancing act of preserving the value of players' collections while keeping the game (somewhat) affordable and having enough cards in circulation to meet demand. I don't know what an "ideal" price for Tarmogoyf is, but I'm pretty sure it's a lot less than $200. I'm sure they'll reprint it (again), but it probably won't be in great enough numbers to really make it tank. But anybody that buys them in the meantime would be dumb to think they'll be $200 forever. Anybody who got them for a fraction of that price back in the day should be happy they got theirs on the cheap, even if the price drops before they sell them (still at a handsome profit most likely).
Like any price bubble, knowing exactly when to get out is tricky. I would have thought it was wise to dump Goyfs and Bobs prior to Modern Masters, yet here are, in a world where those cards got reprinted and the prices eventually doubled. I would have thought selling Underground Seas when they hit $200 was a good move, but now they're $300+. Something has to give eventually; there are only so many greater fools out there. Having said that, even though the market is pretty irrational, you can make certain assumptions about what will be reprinted, and more importantly, how they'll be reprinted. R&D has stated that cards like Goyf, Bob, and Clique are probably too good for Standard, which is why they got reprinted in Modern Masters instead. Reprinting them in a Standard legal set would have surely dropped the price, especially if they were regular rares instead of mythics. Thoughtseize is the perfect example of this; Scavenging Ooze and Urborg are good examples too, as is Mutavault to a lesser extent. Cards that get reprinted in special products don't drop as much, Conspiracy being a weird exception since it was designed to be drafted and thus a lot of it was printed.
Anyway, if you're not playing competitively, I think now is probably a good time to sell. In fact, I'm considering selling my Legacy cards even though I really like the format. Legacy tournaments are few and far between, largely because of the reserve list. The financial barrier is just too high for most new players. I would also sell my Modern staples if it wasn't for the fact that it's my favorite format and I play it a lot.
Speaking of Modern, I really like the addition of Onslaught fetches to the format. It could potentially bring some new contenders to the mix and shake things up a bit, which is a hard thing to do due to the size of Modern. I'm looking forward to seeing what comes out of it.
From a draft standpoint, Khans seems like a good format from what little experience I've had. The abundance of color fixing, flexibility of morph creatures, and high number of playables means you don't have to commit to your colors early on (or at all, I've seen people play 5 colors). I like this; to me drafts are more interesting when you have to decide what to cut at the end, as opposed to trying to figure out which marginally playable cards you have to play to round out your deck. Having more playables also lets you take more sideboard cards, which is also a good thing in my book. Also, drafting a set that has cards you actually want is a nice change of pace!