Unfortunately the only people who can tell you whether or not a revision may be covered is your insurance company. I'd start there if you can't afford to self pay.
Coverage varies as it's dictated by the entity sponsoring the insurance plan. The best way I can explain is, I worked for one of the largest health insurance companies at the time of my rny, in medical review, which ironically we reviewed bariatric surgery.
While a lot of our clients had patients with set criteria, our own employees at the time, it was clear cut exclusion in 2001, at the time of my rny. At the time I had gotten a lot of misinformation because I live in MN and in 2001 (it changed in 2003) that if a health insurance company was headquartered in MN, they had have a different company administering the health insurance plan.
Clarifying, I worked for UHG in Minneapolis, had Medica in 2001. Bariatric surgery was an exclusion for all UHG employees in 2001. Unfortunately when I called the 1st 2 times, I was told it was covered because it was covered with review and set criteria in 2000 and again in 2002. Because I called 3 times, and was told that last time that it was an exclusion, I had to appeal and I lost.
While dealing with health insurance companies is not as confusing as my scenario, it is good to call them and if you have coverage manual for 2017 for your particular plan, to read it.
I know this didn't help much. The only thing that can also be confusing in your situation, is that most bariatric surgeons's offices will not make an appointment without verifying coverage for the office visit. But you can't assume just because the office visit went through and they scheduled the diagnostic for the egd, that it's covered, to protect yourself from surprise medical bills, you might want to ask if that coverage is for follow up versus the potential of you being able to have a revision.
Not saying this to be a pessimist. Saying you don't want surprise bills just starting out for all of this, if a revision is going to be an exclusion.
I hope this works out the way you want it to. Keep us posted...