Do they even make the 709 anymore? I never hear anything about them now. I suspect Czechbiker is right, it's a marketing ploy to move out old stock.
The PT709 has been discontinued and replaced by the G2S, the latter being a single stack version of the G2C.
I expect this was done to slim down the product line a bit, as the G2S will share most all parts of the Slide assembly of the G2C.
I think it was not a great move, as the PT709's Slide profile is nicely slimmer and the G2C shares quite a few internal parts with the PT709.
While I readily admit to carrying my pre G2 PT111 Millennium Pro more, I really do like my PT709's slimmer profile and have a really nice Pocket Holster for it that conceals well.
My PT709 is also noticeably lighter than my PT111, when either are fully loaded.

Taurus PT709 with spare Magazine