The following is taken from PEU1 260.2:
'If it is true now that...'
We use will with if when we are saying ‘if it is true now that. . or ‘if we know now that..
If Ann won’t be here on Thursday, we'd better cancel the meeting.
If prices will really come down in a few months, I'm not going to buy one now.
But I don't quite understand how these two examples are different from the following:
If Ann isn't here on Thursday, we'd better cancel the meeting.
If prices really come down in a few months, I'm not going to buy one now.
Any semantic difference implied?
And I think the first example in PEU could also be interpreted as "if Ann refuses to come here on Thursday, we'd better cancel the meeting". I think it's ambiguous. What do you think of it?
1. PEU = Michael Swan's, Practical English Usage.