On a different note, I've been thinking about the future of Khans block, seeing as only one set of the block is wedge-focused (which leaves the rest of the block completely unknown).
My prediction is that Fate Reforged will be an enemy-colour set, and Louie (Dragons of Tarkir?) will be a shard (i.e. the other five three-colour combos) set. My reasoning:
Although Khans is the only wedge set in the block, I think the multicolour theme is likely to continue - I can't see them making the block themes inconsistent like that.
Khans and Louie will never be drafted together - this was one of the keystones of the block's design. This means their themes are very likely incompatible in some way, such as wedges vs shards.
Fate Reforged is designed to be drafted with both sets; in particular, the draft formats are FRF/KTK/KTK and Louie/Louie/FRF. Notice that FRF is drafted before Khans, but after Louie. Enemy colours in FRF and shard colours in Louie fit this perfectly - each enemy colour pairing is in two wedges, but only one shard. This gives you choice in FRF/KTK/KTK, while drafting it last means being locked into a single shard isn't a problem in Louie/Louie/FRF.
The block has been officially stated to be a time-travel block, with many people speculating that Louie will be set in an alternate timeline of Tarkir where dragons still survive. Nothing says 'alternate timeline' like switching between wedges and shards (just ask Numot and his Planar Chaos buddies).
I think morph is likely to remain throughout the block, being quite a complicated yet interesting mechanic - one of morph's primary functions in Khans was to make three-coloured cards easier to play, so a shard set would allow it to reprise that role. I wouldn't be surprised (though I would be a bit sad) to see morph as the only mechanic from Khans that returns in FRF, making way for five new mechanics in Louie.
Interestingly, although enemy-colour duals are much more powerful in a wedge block, we got ally-colour fetches in Khans. Coupled with the fact that Wizards have stated that they intend to complete dual land cycles within blocks, I suspect this is because they're saving enemy-colour duals for an enemy colour set - Fate Reforged.
We've already had a shard block, but notice that one of the things that's been pointed out about the wedges in Khans is that they're not focused on their central colour - doing the same thing for shards would lead to mechanics very different than the Alara block's.
Finally, Sarkhan and Ugin are both connected to Nicol Bolas in some way. For being such a major character in the story, Bolas hasn't made a personal appearance in a (non-core) set for six years; I think it's likely we'll see him again soon. A shard set on a dragon-themed plane, where two of his nemeses have already appeared (three if you count Sorin, who might not know of Bolas's involvement on Zendikar) would be the perfect place for Bolas to turn up again.
/speculation