Pretty much all of my information on timing comes from hearsay - I don't often interact directly with manufacturers - so take everything with salt.
Endorphin Pro - I believe that it's been pushed to 7/1 to align with the Endorphin Speed and Endorphin Shift. Will update if I hear otherwise.
Adizero Pro - Still targeting spring/early summer, from what I understand, but supply chain delays have made it malleable. We don't have them for testing (at least as far as I know) but they are up on Running Warehouse as a pre-order.
New Balance RC/RC Elite (don't know the formal name) - Hearing late summer/fall on this. Unconfirmed. New Balance was messy even before COVID-19 just in rushing for the World Athletics deadline, so I don't know where it ended up exactly. Know some Trials runners on my team were unable to get pairs before the OT.
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Regarding comparisons - the FuelCell TC is a trainer I did not get sent for review (though we did do a full multi-tester review) but is getting asked about so much that I'm going to buy a pair when they come available. Hopefully Sam or others sees this. The Endorphin Speed and Shift reviews are in the final stages and should come soon, so there should be some comparisons at the bottom of those. Sorry I don't have more for you.