There's always the possibility there's a wired/wireless USB print server that's compatible w/ your printer, particularly if it's an older one. Doesn't have to be wireless, it could be wired, because you can always convert a wired device into wireless w/ a wireless bridge. But having wireless built-in would obviously be preferred, both for simplicity and cost reasons.
Another possibility is a router based print server. For example, I run my Brother USB laser printer off an ASUS WL-520gU wireless router (which has a USB port) w/ third party firmware (tomato). IIRC, the ASUS stock firmware also supports USB printers. I prefer tomato because it let’s me configure the router as a wireless bridge. While it does work, it only supports basic printing. All-in-one features (scan, fax, etc.) are not supported.
Another possibility is using a USB network hub. You connect the hub over ethernet to your router and then plug your printer into one of its USB ports. In effect, the wireless connection between the client and router acts as a “virtual USB cable”. And here too, you could make it wireless between the hub and router w/ a wireless bridge. The big advantage in this case is that you retain the all-in-one features, however, these devices tend to be quite expensive (>$100).
So yes, technically it could be done, but the problem is the potential complexity of configuration and cost. It's like a lot of things in the world of technology; just because you can doesn't mean you should. At some point, it just makes more sense to get a new printer, esp. when you consider how much prices have dropped over the past several years, even for network capable printers. But I know sometimes ppl have a favorite printer they just don’t want to give up, esp. if they have a closet full of printer supplies that would otherwise be thrown out.
So if you insist on pursuing it, and if I was to make a recommendation, it would be an inexpensive router that supported tomato third party firmware. You’d configure the router as a wireless bridge and plug in your printer. And while you’d only get basic printing capabilities (which may be all you really care about), it would remain cost effective (maybe $20-30).