If we look at how the Patriots played, they often had a 4 man front. Typical alignments were 425, 335, and 326. But they played a 4 man front a lot. The more common point is that they did not play 3 LB's very often, but rather played Nickel (5 DB's) as their standard defense and Dime (6 DB's) very often as well. The LB corps consisted of 2 LB's more often than it did of 3 LB's and not just because of down and distance. IMHO, this defense de-emphasizes the LB's as a position, and utilizes LB's as combo players.
They're viewing McMillan in the Donte Hightower role and Baker as a coverage/blitz LB. The pieces we add will likely be edge pieces that can play a hybrid 4 man line DE and a 3 man line OLB. Since neither of our current LB's fits that hybrid role, they're calling them ILB's, despite Baker clearly being a 43 OLB.
Regardless of what they say right now, just remember, this is the time of year when every coaching staff plays the shell game of disinformation, misdirection, and bald faced lies to avoid revealing their draft plans. I can definitely see them keeping McMillan and Baker, but I don't trust anything they say now. After the draft, if they're still singing the same tune, it will be more worthwhile to hear.