I'll be honest, losing those witty Codecs is going to hurt; I'll miss them.
However, there are a few other ways in which it could be replaced:
- Doc Louis and Little Mac are one of them. This would be particularly fitting on the Boxing Ring stage and they would discuss their enemy together. The enemy's appearance, unique attributes and possibly the enemy's origin could be discussed between the coach and boxer.
- Pit in Palutena's Temple is another possible option. Pit would call upon Palutena, who would use her divine powers / knowledge to give Pit the scoop on all of the fighters. Palutena is often portrayed as a chatty-Cathy so to speak, so this wouldn't surprise me; this scenario would be the most likely of the ones I have here, given Sakurai's bias.
- Star Fox could have something of this sort, but the majority of the interventions of Slippy and the gang are battle logs, no knowledge about enemies was conveyed in Melee / Brawl. So I don't see this scenario likely, especially seeing how deprived Star Fox is this time around.
- Fire Emblem characters is another possible scenario, where Chrom and a few others appear on one of the FE stages to give tips about the enemy.
- I'd be absolutely ecstatic for an old-school Cranky Kong pow-wow where he comes out of his cabin on the Donkey Kong stage, complains about the racket going on, insults everyone on the stage with witty comments, and then gives a little insight on the enemy's past to either Donkey or Diddy (or both) Kong. Sadly, this is a pipe-dream, I don't see this happening. The old Cranky seems to be gone with the wind of Rareware.
- Shulk and his friends is another one, although I don't know enough about the Xenoblade series to know what that'd be like. The little I've seen of the cut-scenes though suggests that something could definitely be done here though.
I'd prefer the first or fifth scenarios personally, but given Sakurai's boner for Pit and Palutena bias, expect the 2nd one, if anything at all. There is a chance that the 4th one with FE characters could happen though.