I'd much prefer a Metrotitan to be a retail release. The figure's already worth an arm and a leg as it is.
As for Metrotitan being too obscure for a retail release, consider how IDW is currently dishing out the whole "Metrotitan" deal in a much more mainstream degree than the old Zone toy character was.
And recall how the Energon toyline gave us an Omega Sentinel toy despite that character being a similarly obscure concept being brought to form as a Supreme toy.
Hasbro's very likely gonna want to get the most out of this mold that they can, and redecoing it into Metrotitan would be an excellent AND feasible way to do so. And by releasing it as a retail figure instead of a con exclusive, it would reach a much wider range of consumers: Older fans who know of the Zone character, newer fans who read about the Metrotitans in the IDW comics, and fans who just want a big, nice-looking, colorful toy.
And if the Combaticons have taught us anything, it's that "colorful" = "Retail friendly".