In Preferences → Bundles you can sort by “Updated”. If you do this, what is the most recent bundle you see (my list is shown below)?

The list is regularly updated on disk, to check when it was last updated, please run this in a terminal and provide the results:

    xattr -l ~/Library/Application\ Support/TextMate/Managed/Cache/org.textmate.updates.default

I would think that the most likely reason for not keeping it updated (if you haven’t disabled bundle updates) would be network error (perhaps related to SSL certificate validation or firewall).

To see potential error output from TextMate you need to https://github.com/textmate/textmate/wiki/Enable-Logging — after this run the following and relaunch TextMate to force checking the bundle index:

    defaults delete com.macromates.TextMate.preview lastBundleUpdateCheck