Some of the consequences will be near immediate, for example for travellers in and out of the UK - UK citizens travelling elsewhere may be subject to stricter processing and restrictions on entry, stay, etc. (up to foreign authorities) while foreigners entering the UK may similarly experience changes (up to the UK authorities). There is likely to be some confusion as airlines, ferries, trains plus the immigration officials have to deal with huge numbers of travellers who have not been informed about what to expect. This part of the consequences has me thinking that there will be more chaos at the UK end because (unlike everywhere else I know of within Europe) there are no record systems in place that at the UK border instantly recognise legitimate foreign UK residents.
Other consequences, such as trade, health service capabilities, food availability and cost, etc., etc. will take years to fully emerge. Those who point out that nobody really knows the full story are correct. Promises have been issued to the effect that from 29th March the UK is heading for a bright new future, it's never been so good, "we'll show them" because the rest of the world is going to flock in fawning to beg the UK to allow them to receive the UK's blessing. I am unconvinced and (as I have previously said) I will watch with great interest.