Are you sure it's TU17? I didn't think bugfixes were considered Title Updates...
Prior to TU16, the bug fixes were numbered in sequence also as TUs (see console version history - http://minecraft.gamepedia.com/Console_Edition_version_history ). More recently, however, the numbering system has become somewhat confused since the last small update adding Xbox One transferability (Released on the Xbox 360 on September 4, 2014) was numbered TU17 by 4JSteve (see title on Official Bugs List pinned thread) but remains unnumbered on the Version History page. In addition, I believe the next update being discussed is being called TU20 (for all consoles). We'll just have to wait to see where the numbering system falls out whenever the next one is released.
I've seen nothing official calling the next update TU20... just referenced in a thread by another user and only marginally questioned the source at that. (From: Title Update 20 For All Platforms)
If you have an official link confirming that the next update will be TU20, I'd appreciate seeing it.
Sorry - Didn't mean to imply that it was officially known to be TU20 - just that here on the forums it has been referred to as TU20. The bottom line of my post is: a) that bug fixes have, in the past, been numbered as TUs; and that since TU16 and the release the game on additional consoles, the numbering has gotten a little muddled in people's minds here on the forums and that it was, apparently, even a bit muddled in the minds of employees at 4J (noting the discrepancy between the official bugs thread and the version history).
I'm sure that the numbering will again become clear to everyone whenever the next feature-adding update comes out.
PS3 doesn't use the "TU" format for it's version history. So for the sake of consistency and cross-referencing perhaps 4J (or MS) plan to begin a fresh "re-numbering" of the Title Updates that would apply to all platforms, since it has already been announced that they will all update at roughly the same time. Presumably with the same content across the board.
Projection : TU20 would be considered "TU zed" ; TU21 = TU1; etc.
I thought I saw a 4J tweet that mentioned TU20. I'll edit post if I can find it.