Like Jax says you can update ownCloud in the existing appliance (the specific instructions are here).

To address your original question though, yes an updated appliance library will be released at some point. As a general rule, Turnkey releases roughly every six months, although sometimes those release timeframes stretch a little. No clear timeframe ATM but I would expect a maintenance release within the next few months...

just use this script: http://pastebin.com/UHH9MLVD