AppleInsider reported today that "Q87" is coming. It is described as "an update to an existing desktop computer that the company targets at both the consumer and education markets".
While AI postulates that it likely is the Mac mini with Mac OS X 10.4 Tiger, we think it's probably an updated eMac. Think Secret states that the Mac mini is Q88, and Q86 is the current eMac. Thus from the numbering system, it sounds like that Q87 is in fact a new eMac and not a Mac mini. A new eMac is expected anyway, since it has already been 51 weeks since the last eMac revision.
The new eMac will likely also ship with Tiger, given that Tiger has already been declared gold master.