According to Sony Japan, the upcoming Sony FE 300mm f/2.8 GM OSS lens now already in short supply before official release date on February 23rd. If you pre-order this lens now, you may wait 6 months to get this lens in hand.
From Sony Japan:
*We have received far more orders than expected, and the current estimated delivery time for orders is 6 months or more.
Sony FE 300mm f/2.8 GM OSS Lens Pre-order at Amazon/B&H Photo Video/Adroama.