I will be replacing my 27 year old 200K btu Lennox G11 furnace this summer with a Trane XV90 120K btu, and it has been suggested to replace the inside A/C coil at the same time. A previous homeowner had the outside unit replaced due to hail damage, but they reused the original 27 year old inside coil.

Currently the outside unit is a 5 ton, while the Manual J is showing 4 tons should be right for my house. Knowing that I will eventually have to replace the outside unit, is it possible to use a 4 ton inside coil with the existing 5 ton compressor? My thinking would be that when I downsize down the road I wouldn't have the added expense of another new coil. Or is this just a wasted thought on my part?

Not being in the HVAC field, I thought you guys would be able to help me understand any problems with my train of thought.

Thanks in advance for your ideas.