This caveat makes me wonder if the premillennialist view of Calvin's day wasn't different than the view of today? If so, then Calvin's comment may have been accurate for its day and the premillennialist's view was modified to negate Calvin's argument. Once modified, it could be claimed that Calvin was in error which would be a bit disingenuous.
I strongly suspect that's the case.
The Charles Hill book I've been recommending looks at millennial interpretations in the first centuries. One of the interesting things he finds is that pre-millenialism in that era tended to be tied with a view of the intermediate state that we would find unusual -- that all but a special subset of special Christians, spent the intermediate state in the "good part" of Hades.
The old guys didn't always fit our modern categories well.
(More apropos to the dispensational eschatology question, I think, is Calvin's pair of chapters in the Institutes on the differences between the testaments and the similarities. There he's dealing with an opponent (Servetus, I think) who held that the OT only promises material, this world and this life, blessings. Not a position you see these days.)
This is what Theopedia states:
Premillennialists fall into two primary categories: historic premillennialism and dispensational premillennialism. Historic premillennialism is so called because it is the classic form which may be found in writings of some of the early church fathers (mentioned above), although in an undeveloped form. Dispensational premillennialism is that form which derives from John Nelson Darby (1800-1882) and dispensational theology. It is dispensational premillenialism that first taught the notion of a pre-tribulation rapture.
Historic premillennialists reject the idea of a pre-tribulation rapture and the uniquely Jewish nature of the dispensationalist's millennial kingdom (see below). It is often assumed that all premillennialists are dispensational in their theology. This is a confusion that should be avoided. Historic premillennialists such as George Eldon Ladd are consistent Calvinists who did not accept the basic tenets of dispensationalism.