Imports will increase. But the pressure on the balance of payments will be offset by increased capital inflow and by more exports. The liberalization programme will bring a lot of new business opportunities. WTO membership means that China would commit to a timetable of liberalization. But an agreed timetable would mean more certainty for businesses.
Uncertainty is bad for investments as it makes long term planning difficult.
The current WTO accession talks do not address very much these problems. To the extent that foreign investors in general become more optimistic about China's medium term economic prospects, there would also be more business interest in China and more investments. The other side of liberalization is the increased pressure on the Chinese enterprises in general. Enterprises have to restructure, modernize and get to their senses faster if they want to survive. Those unable to do so will have to face the inevitable.