I worry less about them doing anything directly to WHM, to be perfectly honest. Aside from feedback, they also look at the data on their side before changes are made. So it's not like a bunch of players can go "Omg, WHM's healing numbers while dpsing are amazing while SCH and AST can't even keep up in either department!" unless there's data on their end that backs this up.
That said, I am wondering about how they can affect us indirectly. SCH and AST seem to be having a hard time in general, despite Yoshi stating that he wanted all three healers to remain viable. In 8 man content where we have 2 heals per a group, a good dynamic would be a WHM + one of the other two for either more dps (SCH) or more raid support (AST). If they try to equalize that so that SCH + AST is a good comp, a good number of people would probably get pissy.