First time poster and TVPaint user here so be gentle

I have a few questions about which recommended resolutions we should work in and how will it effect the output down the production line.
I am new to TVPaint and have worked previously with Toon Boom and other vector based software.
The situation is as follows:
We are about to start production on a feature film and we are currently trying to figure out if we should work in a 2K or 4K.
We have some people in our team saying that 4K is a waste of time and resources and that we should just focus on working in 2K.
I personally feel that it would be shame not to have the source project in 4K and export it to to 2K.
I am confident our systems will handle it, 16gb of RAM, i5 processors and a 1TB drive @ 7200 RPM and 15TB of server storage, and working with proxy's.
Now I have been reading up on the whole 2K vs 4k Digital Cinema debate and I know people wont see the difference after a certain amount of distance, etc, etc and that the whole 4K resolution is marketing sham and its about frame rate and bitrate rate, etc etc...
But it still somehow bothers me knowing that the industry is now pushing for this whole 4K Home Cinema experience, and when the film will be done in 2 years that we wont be able to experience the movie natively in 4K on home screens and displays some time down the line.
The 2K camp believes that it wont matter because up-scaling will solve this problem or that we just render the 2K source at twice the size.
Now correct me if i'm wrong but up-scaling bitmaps from 2K to 4K will cause artifacts, jaggies or other distortions to the animators lines and background artist's scenes? Isnt the 'rule' working with bitmaps always to go from large resolutions down to smaller ones?
So in summary what would be a better situation:
Have all source material (animation & backgrounds) in resolutions 4K and up?
Or just have all our source in 2K and believe in up-scaling and that we can re-export the 2K frames from TVPaint to 4K?
Thank you for your time and look forward to hearing from you!
W.
Work Environment:
Windows 7 64bit
TVPaint 10 Pro 64 bit
Workstations:
Core-i5-3570-3.4GHz,
16gb DDR3 1333Mhz RAM,
GT 640 video card 2GB
1TB drive