Looks like Dumball's Road plans are progressing, but it will be a long time before a spade is in the ground:
https://cardiff.moderngov.co.uk/documents/s24864/20181011%20Vastint%20Cardiff%20Scrutiny%20committee.pdf2,000 homes, office and commercial space, for a total quantum of 3,700,000 square feet or so. Anticipated first homes in 2022, with an 8 year build-out period for the whole site, so overall completetion in 2029. So complete in a little over 10 years time.
The proposal is for mostly 6 - 8 storey blocks, with larger blocks on the riverfront and at "key points" - which seems to be Penarth Road, and on corners on Dumball Road itself.
Outline planning permission expected in a few months.