There has been talk (mostly by politicians with no budget) about this sort of thing for ages. Latest was a newspaper article a few months ago http://icwales.icnetwork.co.uk/news/wales-news/2008/04/18/plan-for-wales-to-get-channel-ferries-91466-20782350/ but even with the most optimsitic spin they gave a date of "as early as next year". The article also included a quote that they were trying to get finance (they've picked the wrong year for that!) and there is also the question of fuel prices which must affect their budget. From what I can make out the vessels quoted are passenger only and I don't see how they can fill a regular service between Swansea and Ilfracombe.

So, looks like you are going to be using the bridge which will at least be a bit of excitement for the kids.

There used to be a paddle steamer The Waverley that went from Penarth near Cardiff, to Minehead and somerset.
I thought it had stopped but I found this website, I think it's was foot passengers rather than car ferry
http://www.waverleyexcursions.co.uk/bdisp.htm?port1=porthcawl&port2=