The file-system calls that PSE7 is using don't use big enough numbers to hold all the digits in 3TB.
As to your question whether PSE12 does, I'd guess so since PSE12 has been out about a year and 3TB drives have also been available to consumers about that long if not longer--6TB drives are available, now, in Best Buy, so you'd mostly likely be fine, but if past history is any guide, and with the cloud it may not be, PSE13 is due out any week, now, so if you aren't sure, then wait until you can get it and be more sure it'll work.
You can certainly download the PSE12 and run it as a trial for 30 days to make sure it'll work and then buy PSE13 assuming it comes out in less than 30 days. PSE12 was released Sept 23, 2013.
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One way that sometimes works to trick old software, like PSE7, into working would be to make your free space just slightly less than a multiple of 512GB but creating some large files or copying some large folders of files to temporary copies, That way the old program sees just slightly less than 512GB available and won't complain.