Who knows?
But it seems to me that now that running homebrew on the newest FW is possible, it makes looking for a kernel exploit much easier. So at least now there's a chance it will happen eventually, unless everyone loses interest in the 3DS before then. It could take years or it might never happen.
Gateway has been pretty quiet lately, maybe they've found something. After all, it wasn't long after Ninjhax was released before Gateway Ultra showed up out of nowhere. That's just speculation though.
I think as long as there are skilled hackers working on it, eventually an exploit will be found. It's not impossible to make a 100% secure system but it's very very difficult. Originally the 3DS was thought to be extremely secure and that's been proven not to be the case, so while they may have patched up some holes I wouldn't be surprised if they've missed some. There are already several known kernel exploits, there are probably more where that came from.
For all we know, skilled hackers like yellows8 may have already found kernel exploits on newer FW, they certainly wouldn't tell us if that was the case.