I'm not going to get a Surface, but to be clear every singe app that I currently use on Windows is definitely going to be available at launch on Windows RT, assuming you count Chrome and IE10 as interchangeable (which non-experts do) or if a version of Chrome launches (like the version on iOS). It's going to launch with a browser, a chat client, a media player, and a random set of games. There is nothing else that I run on Win7.
Anything intended to be used on a touchscreen device needs to be written from scratch. Any application intended to be used by a mouse used on a touchscreen is an absolutely awful experience (I used a WinXP laptop with a touchscreen display about 6 years ago, totally fine laptop but the touch screen is useless because the usability in apps is not there). You can't expect to just run Lightroom on a touchscreen and expect it to work well.
I had never heard of Lightroom before, and correct me if I'm wrong, but it looks like it is targeted at professional photographers or hobbyist photographers who have $1000+ camera equipment. I dual boot Ubuntu for development, and I recognize that is esoteric hobbyist usage, and I don't expect Windows to start supporting all the tools I want for development out of the box. I can't imagine who really thinks that level of usage should be supported by a low end consumer device.