Some rumours I've heard:
1. Empire is going to be the next but one or two, probably April next year (Vamps in Jan, so maybe another in feb or march).
2. We're also due a WD update like the Vamps got in the summer. This will probably include a new war altar and new warrior priest rules, including (and this is the bit I'm really excited about) priests of ulric and morr.
3. I've also heard of a new war wagon, demigryph cavalry and priestess of myrmidia, but I'm not sure whether these are due in teh update or just in the army book.
What I'd like to see:
1. custmisable knights, a bit like the maneaters with their "pick two special rules", although possibly some variable +1 stat options, so that you can build your own knightly orders. I'd also like to see the fluffy orders specified as to what rules combos they get, but perhaps a point cheaper as a result.
2. Halflings - I like halflings, and they're there in the fluff, but I'd like to see them done with a bit more grit and a bit less of the "comedy fat man". My suggestion would be skirmishing sling guys, like the field wardens in 2nd ed roleplay (they might be in the other editions too, but my knowledge is limited to 2nd)
3. A war altar that you can push around with a unit of flagellants like a screaming bell (but possibly this is just because I have one as a conversion).
4. minor fluffy bonuses for different regions, possibly that you had to swap the detachments rule to make use of, possibly attributed through special characters like space marines special characters. For example, if you select johnny forrest, a talabecland special character you can choose to give all the units in your army the forest strider and river strider special rules, but if you do so they cannot make use of the detachments special rules.
Cheerio,
Ben