It's doubtful, but you never know. Remember, the original proposal for MSHI was DC. You can find pictures of the materials online, they sold on ebay a couple years ago. The idea was developed while the Six Flags deal was in place, so I wouldn't say the licencing agreement alone would preclude this happening. I don't know if Six Flags has the same exclusivity and perpetuity provisions w/ DC that Uni does w/ Marvel. Also, the very successful partnership between Uni and WB have had w/ HP could "grease the wheels", so to speak.
That being said, despite the licensing revenue going to their closest competitor, I think Uni is quite pleased w/ the profitability of the Marvel properties and isn't in a rush to replace. I don't think the DC characters bring quite the same level of revenue and popularity as Marvel.
Certainly nothing will happen w/ DC while Marvel is on property.