The Emirates naming rights deal was signed in 2013. The thing is, though, stadium naming rights deals really haven't grown much, if any, in value since that point and their deal remains pretty much as high as they go. If you look up the most lucrative deals in place today, you'll find a bunch of capital city clubs that usually play in the champions league, Bayern, and related parties deals. A lot of people out there will speculate stuff like that old trafford's could go for 30M or something, but then those deals never happen.
One of the biggest deals in football was also actually signed in 2013 with Besiktas, 10 year deal with a 5 year option. I'm not sure whether it was the club or the sponsor, but their stadium does not seem to carry the sponsor's name anymore, so it looks like it was not extended and now the stadium has no naming rights sponsor. I'd be shocked if the club turned down free money on this one.
I'll be very happy to be wrong if somebody rolls in with a giant offer, but all signs point to that market not being particularly strong, especially for clubs that aren't in major international hubs and are regularly on the wrong end of the table.