This is FUD.
Sony has been using the terminology "Driveclub" (retail and digital, identical) and "Driveclub PS+ Edition" (digital, PS+ only) to describe the two means of acquiring the game. If they had not been specifically referring to two different versions of the game, then what you say would have merit; basically, you have to wait for your sub to lapse before you can buy the digital non-plus version of a game that is currently freely available.
That is not the case with "Driveclub" because it is not a free PS+ game. "Driveclub PS+ Edition" is, and will never be a full retail/digital game, so there will never be this particular collision.
It seems like they are treating the upgrade as DLC, not a separate game. So if you have the PS+ edition, then you do own Driveclub as part of the IGC (a free PS+ game). If you own a game as part of the IGC, then you can't buy it digitally.
The official comments have been ambiguous, and have avoided saying that if you have the Plus edition downloaded you can then opt to get the non-upgrade, digital version.
"My recommendation would be to give the FREE PS+ Edition a go when it comes out in October to see what you think of DRIVECLUB. If you like it which im sure you will
![Smile :) :)](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
then you have the choice of upgrading or just going out and buying the Blu-ray to get all of the content in one go."
He specifically omits the option of getting digital for someone who already has the Plus edition.
So as far as we know, based on the info available, unless specifically stated otherwise, a person who downloads the Plus edition can NOT then get the non-upgrade digital edition.