The EU will treat Britain like Greece

[bhikkhu]

14. Paradigm shifts do happen

As the UK economy is built on trade, and about 50% of that has been with the EU, a change in trade could lead to a long term shift in economic trajectories. As well, about 50% of UK capital financing comes from the EU region.

http://webarchive.nationalarchives.gov.uk/20160105160709/http://www.ons.gov.uk/ons/rel/international-transactions/outward-foreign-affiliates-statistics/how-important-is-the-european-union-to-uk-trade-and-investment-/sty-eu.html

I don't know enough to predict anything really, and you may be right, but nations do go up and down based on their economic decisions. More often in my lifetime they go up, as it typically doesn't take much economic pain from a bad decision to collapse a boneheaded government and change course. But its hard to say how easy that would be in this case...it might be years of dithering uncertainty (which the markets tend to punish), by which time things could be very different in the UK.