I'm not sure you understand the capital infrastructure required for a game like Destiny. Unless they are willing to invest a literal dump truck full if money into servers and development they won't make an MMO. Especially after they see the reception of destiny.
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The capital investment is fairly easy to obtain for proven developers especially for a game that already has a following. Gearbox have various connections with big publishers including Valve and Microsoft, both of which are likely to have an interest.