The biggest issue for the tenant might not be the need to find somewhere else, but the inconvenience of having to accommodate viewings. So worth thinking about that.
It may not bother them (initially), but if it gets to be a burden on them and you want to keep them in there until the sale goes through, you might have to consider some inducement, like a rent rebate (not a reduction) while the viewings continue.
Also, bear in mind you might (although unlikely at present) sell it to an investor and the (good) tenants might be an asset and you would want them to stay in that case.
I said rebate because in case of the sale not occuring, you want to be able to end the rebate and if selling to an investor and tenant is happy to stay, you don't want to sell on with a reduced yield.