I cared about T5 even when I was a Star Alliance flyer, now I'm mostly a BA flyer I care about T2 for the same reason.

Although T1 is nothing special now, it was a lot worse when it was a major terminal for BA. Once BA completed the move to T5 it was more pleasant for BA pax, but also more pleasant for those still left in T1 and those that moved in from old T2 (bmi, Lufthansa etc). Same with T4 and SkyTeam.

So a successful T2 launch will see space being freed up in T3 which will make the BA operation there much more pleasant (no more bussing hopefully) and will mean BA can move out of T1 once more.

Also as some times we need to use other carriers it'll benefit us then too