Well it's happening. Germany is sending 14 Leopard 2 A6s to Ukraine and allowing third parties to re-export their own Leopard 2s to Ukraine.
It's not certain how many will arrive, so far nations are each pledging about a dozen or so apart from Spain who pledged 53. But we don't know when these are going to arrive and how far this goes, Germany said 3-4 months.

The problem is that while their are many Leopard 2s available to send on paper these tanks are mostly in various forms of storage and are in varying states of repair. Many would need extensive refits before being sent.