Eh, it probably means he just wants to retire and either there won't be an SE6 or it will suck horribly...
But really, did we expect him to keep working on Space Empires this long? I was a bit surprised even to hear the official announcement of SE5
Still, I fear that Strategy First might be about to "Crisium" Malfador - i.e. buy out SE5 and then just drop any plans to publish it, much as happened to Crisium's Stars! Supernova...
It makes absolutely no business sense, though, unless they're developing something of their own which might compete with SE5... in which case we might just be in for a treat rather than a disappointment... you never know...