Are you saying smart playlist no longer updates (when a podcast is played) on the iPod? It still updates when played in your iTunes library, correct?
There's been a recent change to the Edit Smart Playlist settings window. At the top of settings window, there's a new option to limit the Media Kind to a particular category (see screenshot below after the work Match). Previously, choosing a particular Media Kind was one of your rules. I think this change is what causes the problem you describe.
I set up a test playlist that shows all of my unplayed podcasts. It looks like this with current iTunes.

Note that the setting at the top says Match [podcasts] for the following rules. That top option was not there before, and you needed to have a separate rule like Media Kind is Podcast instead, to limit the list to only podcasts.
What you can try is to change podcasts in the top option to All Media, to not limit selection there, and add a rule that limits selection to podcasts. Unfortunately, if you use Media Kind is Podcast, iTunes changes it back to use the option at the top. So, use a different rule to limit selection to podcasts. I set it up like this

NOTE: Genre is can be anything (or blank), so you'll need to confirm all of your podcast episodes have "podcast" in their entry for Genre. You can select your entire podcasts library at the same time (Select All on it), Get Info on selection, and change all Genre entries (for podcast episodes) to "podcast" (assuming that's OK for you).
This change to All Media, with an added rule to limit selection to podcasts, may make your smart playlist work like it did before on the iPod. I can't test this myself, because I don't sync podcasts (and my iPods are mostly too old to support smart playlists that update on the iPod anyways), so you'll have to give it a try and report back if it works (or does not work).