The definitive answer (confirmed by Ike) is that the 5000 housing will not work for the 5400. The controls have changed, and the size is just a bit differant.
The opinions that the 5000 is superior come from two things (that I've seen, at least) A) No RAW/NEF. Well, the 5400 will get a firmware upgrade to add it, just like the 5000 did, according to most sources, so that may be a non-issue. B) It can't use the E68 wide angle lens. True, but if you don't have that lens it's not a big minus, is it? You still get a much wider view than any of the competitors.
What people are ignoring is this. The 5400 will have an MSRP of $799. That's the current street price of the 5000. When it gets to B&H expect the price to be lower, which makes the current rebate on the 5000 a wash. (in theory) Hmmmm, new camera at last years closeout price. Nice.
With no reviews out yet, I'm not willing to write off the 5400. Maybe they improved shutter lag ... or autofocus ... or LCD brightness ... you just don't know yet.
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Do you know what caused the flood?