Without more information, I can only guess that the warning message is produced because your ports tree is ahead of your -current snapshot.
If you are building ports, then you should understand the meaning of the warning message. There is a significant differences between major and minor library revisions, and there is a reason why the lower minor number is acceptable for that particular port.
See
http://www.openbsd.org/porting/libraries.html and review the discussion of major and minor revision numbers, carefully.