NOT A TEACHER
Swan (Practical English Usage): 91/3 - BE + INFINITIVE (you are to, I am to etc) : pre-conditions: If we are to get there in time....any diference in the meaning
''The structure is common in if-clauses, when the main clause expresses a pre-condition - sth that must happen first if sth else is to happen.
If we are to get there by lunch time we had better hurry. ''
However, because of the future reference of the subordinate clause, I don't see any difference between the sentences either. Moreover, according to the rule it seems rather strange to me to use the second one.
To summarize it, I quoted the 'rule', gave my opinion and now giving advice to wait for someone else's (native) opinion.
Have a nice day anyway
Interested in Language