poly count limit?

I have no insight into RW internals and red51 may answer with more reliability. How I get it is that there is no explicit hard limit on poly count in RW (of course, there are physical limits imposed by the hardware used), but more polygons there are, more the performance will be affected (well, obvious! ).

60,000 seems very high for just one model to be rendered in real time within an already complex scenery. Even 5,000 might be heavy, particularly if you plan to place several models.

There is no real polygon limit, but basically it's as @Miwarre said: The more polygons, the more the performance will suffer. It depends on what you want to bring into the game, and how many instances of this model you want to spawn. If you just have a small chair with 60,000 triangles (keep in mind that triangles matter - some modelling programs use quads as polygons, so in this case the actual polygon/triangle count would be twice as high as), it's definitely too much, especially when spawning the chair multiple times.
If you insert a giant castle model with 500,000 triangles (but there is only a single instance of the castle in the world), it's probably fine. The total polygon count matters. Low budget graphics cards may run into trouble when there are more than 1,000,000 triangles in a scene.

For a reference: Most objects (e.g. furniture) ingame have between 500 and 2000 triangles, trees have between 2000 and 7000 triangles (usually around 4000)