From comments made during Winter Test Media Day:

The GT1 class is not going away. The American Le Mans Series is still a four-class series; it follows the ACO rules and remains affiliated with the 24 Hours of Le Mans. The Series encourages competitive entries to GT1 class; however it does not currently believe there are any such competitors in the pipeline. Therefore, the Series sees an opportunity to create a very competitive GT class within GT2. Additionally, the Series and IMSA will not allow a non-competitive entrant into GT1 class simply to accumulate points and victories due to a lack of competition once Corvette Racing moves to the GT2 class from GT1 after the 24 Hours of Le Mans.

-credit: alms