Major Disappointment So Far
The OP has struck a resonating chord with me. It's April, and we have seen no real announcements about 6th edition. Has GW even officially announced 6th Ed will be coming this year?
We've seen "closing wave" models released for Space Wolves and Bugs that may/may not have been done for sometime, and there is no ETA on Dark Elder offerings to fill that range. Are there any models left/unreleased?
We've received the Crimson Fist anniversary miniature... and that's it. It's all been Fantasy.
A ray of hope- the Hobbit isn't coming out until December, so maybe the game in November/December? We know the releases through April and a good idea of May, so that gives us June-October (five months!) for GW to blast us away with the 25th Anniversary of 40K and 6th Edition with a couple new Codex books. Please GW! Don't let us down!
The same thing happened in 8th edition. . .
I wouldn't call doom and gloom yet. The 6rh edition schedule seems reminiscent of Fantasy's 8th--Beastmen came in Jan (Necrons were Nov) 8th in the Summer (6th coming then). The next fantasy book was Orcs in Jan--a year of no armies. I don't think they'll go that long for 40k--8th had the new book format, and lots of changes to deal with. The experience there should hasten 40k's transition. But I'm not surprised at all that they aren't releasing any more books before 6th. The probable shift to hardcover, and making sure everything they are working on works together is time well spent. I'd rather have a book come after 6th than just before it, since the changes are going to be bigger than that between 4th/5th (or fantasy's 6/7th).
So yes, the first half of the year will lack much 40k. But I'd wager that 2-3 books are out by this time next year.