Firstly there is no guarantee that new owners will be able to afford to build a new stadium in the short term.
Secondly, the current plans are already over two years old, and were probably conceived up to four years ago. Stadium design itself moves on, and it is highly likely that improvements could now be made which were not possible then.
Any new owners will want to review the Stanley Park project That would sensibly include a current cost for the consented 60,000 seater, the comparative costs of building a 70,000 seater now as opposed to upgrading in the future, a redeveloped Anfield, and Groundshare for so long as it is an option. That seems like good business, and common, sense.