I suggest to check out few literature and also check out AGA, AASLD, and
ASGE. The whole field is growing and changing very fast. Remember GI also includes hepatology, transplantation (pancreas, liver, small bowel),
nutrition, ID in Liver/GI, immunology (i.e., treat IBD with chemo/modulator like infliximab, etc.), proctology, etc.
Interventional GI is only one part of of many GI's. It's true that the interventional GI endoscopists nowdays do some of what the surgeons did 5-10 years ago. Endoscopic bariatric surgery ($$ nutrition), partial esophagectomy for cancer using endoscopic cutting and suturing devices, transluminal and extra-luminal procedures including EUS-guided LN
biopsy-staging of cancer, implanting radioactive seed for pancreatic cancer, endoscopic anti-reflux surgery (fundoplication), are very few of many things
developed or under development in interventional GI. Magnifying endoscopes, chromoscopes, small bowel scopes, endoscopic cutting/suturing devices are already available
commercially. GI's also treat IBD with immunomodulator/Chemo like "infliximab" (bills like a procedure $$). A good thing about GI is you can tailor your lifestyle and work based on your interest. If you don't like to do endoscope, you don't have to. You can be specialized in other areas like pancrea, liver, transplant, or nutrition. If you like eveything, you can do all.