Garmin is now selling the 1030 for $449. Usually when Garmin drops the price significantly, it means a new model is about to be introduced.
Yes, they are preparing the release of an Edge 1030 plus (which is not the 1040). It is assumed that it is mostly the 1030 firmware with slightly updated hardware (maybe...) https://the5krunner.com/2019/11/14/garmin-955-745-lte-fenix-6-sport-and-more-incoming-new-garmin-devices-fenix-forerunner-edge/
Keep in mind that those are mostly rumors and guesses.
As a 1030 owner, I would not be concerned about the 1030 plus. As the 1030 is still pretty bugged, Garmin at least tries to keep us updated to the best of their abilities, and it seems to me that the upgrade to the plus version is likely not that impactful. (might be a different story with the 1040 if/when it comes out).
Garmin usually release devices either in April (Edge 1000, 520 Plus 530/830) or in July/August (520, 820, 1030). The only device they've ever released between October and March has been the 510/810 back in 2013. Still, it would be nice to see a faster 1030 with a better screen, as Garmin must be aware it lags behind the 530/830.