Years? IMO, looking at the stats of Western European countries, who are all slowly lessening restrictions, typically showing both carrot and stick (“we think x will be allowed again in w weeks, if you all keep following the rules”), unlikely, at least not for countries with significant tourist industries. They will feel pressure to allow tourist visits, certainly from ‘safe’ regions such as Australia and New Zealand.
(Whether those tourists will go on holiday is another question. Tourists may be wary of going far away on holiday, and if social distancing will be compulsory inside planes, and trains, travel likely will become much more expensive)
It also will be hard for countries to withstand the pressure from their population to allow them to go on holiday in other countries.
In the end, the better choice may be to allow some tourist visits, as that may mean people will follow restrictive rules better than when they wouldn’t be allowed to have go on holiday/to make some money from tourism.