This is one of the strangest arguments that I've seen on a message board as it looks like everyone is talking past each other.
Will the Big East still be a good-to-great basketball conference? Yes. Will it be better than what it was this past decade? Very unlikely.
The fallacy of the argument that just because Pitt, WVU and others rose up in the basketball ranks during their time in the Big East means that the new conference members will do the same is that such rise was dependent upon schools like Syracuse being members (as opposed to simply the Big East label). It was the critical mass of a large number of great basketball teams playing each other at the same time that created an aura around the Big East, but now a number of those great basketball teams are going away (which means that the same critical mass isn't there anymore).
There is also a major difference between the ACC raid of Miami/VT/BC that didn't take any good basketball schools away (and who were replaced by a legit basketball power (Louisville) and 3 other schools with historical basketball tradition (Marquette, Cincinnati and DePaul)) versus the losses over the past year where the Big East lost 4 upper tier basketball programs. The Big East was able to clearly and unambiguously improve in basketball after the 2003 ACC raid, which isn't going to be the case after these latest defections. At the same time, the BCS era of the last 15 years, despite being about football, has fundamentally changed how basketball works since schools such as St. John's, Georgetown and Villanova no longer have anywhere near the advantages in facilities and TV coverage that they had in the 1980s and early 1990s. The SMUs and UCFs of the world can't leverage those Catholic schools in the future in the same manner that Pitt and WVU were able to do in the past.
To be clear again, the Big East will still have an excellent basketball conference. However, no one should kid themselves that the latest Big East expansion was anything other than a triage measure (as opposed to actually believing that Temple and Memphis could replace the value of Syracuse and Pitt). The defections over the past year directly impact Big East basketball much more than the ACC raid of 2003, so it's far too simplistic to believe that the Big East label in and of itself will overcome all of that.