They have to have that spotbeam for NY anyway, for other networks (my, cw, pbs).
The old mpeg2 were on the old 3lnb sat, and the new mpeg 4 were spotbeamed for the local area. When they upgrade the DNS feed to mpeg4 on the new sat and turn off the old mpeg2 version, they then could have just the conus feed. Turning those 4 off on the NY spotbeam may not really do anything for them space wise, it's hard to say. Perhaps if their beam covered another smaller market they want to do HD, or if they wanted to add other stations that they couldn't fit, but at this point anything like that is speculation.
They were originally spotbeamed in mpeg4 on the spaceway sats because the dns feeds were mpeg2 on the old sat, better quality.