I mostly agree with that (though I don't think the divide is on the level of the NI divide and there is also a North-South divide which exists - I think one of Wales' problems historically has been a failure to combine their forces behind one cause) and it's for that reason I put them third most likely of the 3 non-English parts of the UK to split from England. But I wouldn't rule it out if there was momentum from Scotland and NI jumping ship, particularly if at least one of them is successful. I wouldn't expect it to happen in a matter of years - I would imagine it will be 15-20 years at least - but I can see a scenario where it occurs.
England could help it not happen, but if we act in line with some of the more, er, outlandish comments we've seen here then that will be a great way to get Wales to stick two fingers up. I'm not entirely convinced those comments aren't reflective of how some of our politicians think, massive arseholes that some of them are.
FWIW, whilst in land terms Wales is indeed approximately one Wales in size, its population is about ten times that of Iceland and about half a million less than Uruguay. So how much size matters in this case is questionable.