First look at what Apple is proposing as a 'replacement' for Aperture that I've seen:
Doesn't seem like much of a replacement based on this information.
I don't think anyone can call it a replacement. I have been using Aperture since it was released. Pretty frustrating to see Apple drop professional photographers wholesale.
I'm sure Photos
will improve over time but I'm not seeing anything that looks like the understructure for a fully fleshed out pro-capable app.
All that said - I have been using Capture One v8 since early last fall, first for tethering and lately looking to make a full switch. If anything it does show what Aperture might have been - layers, copying and pasting of masks, client review of images in real time via an iPad, etc. It also has much better processing of raw files, something a new Aperture would probably have been capable of had Apple not stopped development.
Review of Photos by David Pogue
which goes into differences between it and Aperture (scroll down.)
I had planned to try and stick it out with Aperture since it will work for a while more but already needing C1 for tethering on jobs (Aperture has become too flaky - a combo of the software itself, the OS, and camera FW updates - none of which are keeping pace with each other) and seeing how much better C1 is at conversions (far less noise, smoother gradations, more dynamic range) there are no reasons left to stick around.