Terry is correct.  Once you converted (uploaded) 2018 Taxwise into Proseries 2018 you simply need to transfer from 2018 to 2019 Proseries.  It is now a transfer not an upload.  This can be done any time.  I would just roll over a few or just as needed as sometimes bugs happen in early January in the transfer process.  Which is probably why Intuit told you to wait till January to transfer files.  I hope everything updated correctly from Taxwise and I wish you luck.