I can only see myself changing brands if my A7 fails and all the worlds new and used Sony bodies have disappeared into a black hole. Other than that I just don't have enough interest in kit fondling to switch brands. This Sony mount kit is enough to keep me with Sony even though I've always hedged my bets and kept film era primes that I could use on just about any new mirrorless camera.
Sony, 20mm f1.8, 35mm f1.8, 55mm f1.8, 85mm f1.8, 35mm f2.8, 28-70mm f3.5-5.6.
Voigtlander, 35mm f1.4, 40mm f1.2, 50mm f2.
There's a lens for just about everything I want there