You can either take out the soffits (my vote) or build out the soffits using studs and sheetrock. How tall are the soffits? If vey short, maybe crown molding could camouflage the gap.

We have that situation on one wall. Before you look at the pics, realize it's still kind of in progress and lots of people here will probably hate my choice. We have 15" IKEA cabinets and we put in an external range vent that goes out the wall to the left. We expressly did not want to go to the ceiling with the cabinets on this wall and wanted the soffit built back, meant to be unobtrusive like a little step. Original plan was to paint wall color. Blah, blah, blah, turned out soffit had to be larger. In the framing of it, the plywood was reminiscent of a rustic beam so we held off on painting to ponder. LOL, it will probably be "in progress" forever. Anyway, you can see if the pics give you an idea of what to expect.

From the side:

Thank you for the photos! I'll show it to my husband and see what he thinks about it.

We're also want to install Ikea's cabinets but now we can't decide it's worth it

For what it's worth, I *love* my IKEA cabinets.

You can take the soffits out and run cabinets to the ceiling.

We thought about taking it out but the problem is that there are some pipes that running through the soffit and it will be much more expensive to reroute the pipes than to add the additional 3 inches.

Everday I learn new things in the process of kitchen renovations.

How much piping? How high are your ceilings.

Many people have pipes running through cabinets. Taking the cabs to the ceiling makes a room look taller to me and gains space for occasionally used items that otherwise take up valuable real estate in the lower portion of cabinets.

If it is uniform it might look ok, (I don't think I would do it) but for some reason, with all of the people that worked on my kitchen, no one realized that the fridge cabinet would stick out about an inch from the soffit until it was installed. It looked terrible. We had the soffit extended about 3" on that wall to make it work. We have 9' ceilings and 24" soffits. We really didn't see any reason to take them out as they have electrical and duct work in there. Ours add visual interest that we liked as well, and we didn't need more storage. Can you post pictures? This probably doesn't help you, but this is after we added it. Will your fridge stick out even farther? We had to make that one 27" to work.

I vaguely recall a reveal or a photo awhile ago where someone had the cabinet doors go all the way up to the ceiling (minus frame and crown, of course), but when the doors were opened, the top "shelf" was just the soffit. It gave the look of full-height cabinets without having to remove the soffit or figure out how to deal with it.

If you are doing custom doors you could make it look like you have cabinets to the ceiling and cover the soffit that way.

I don't think you will notice it much if you leave it as is (painted to blend with the ceiling) with the cabinets 3" deeper than the soffit but you are creating a new area to dust....

Our kitchen is about 9ft (108 inches) and the wall cabinets are about 30''Lx15''D