So consider a noun in Japanese such as 毛皮 that ends in a わ mora. If you were to construct a sentence with such a word as the topic it would have some structure like 毛皮は which when spoken out loud, would have the わ sounds repeated twice in a row. Grammatically, I assume the topic marker は should be included in such as sentence and in formal written language would probably be included, but when speaking, would native speakers drop the topic marking particle in this case in order to sound more natural?
I'm not sure why you are worrying about this, but there is nothing wrong with saying wa twice in succession. It's not unnatural at all. When the topic ends with わ, we simply say 毛皮は kegawa-wa, 川は kawa-wa, チワワは chiwawa-wa, and so on. Nothing special will happen.
The topic marker は is commonly omitted in speech anyway, but that's a different phenomenon that happens regardless of the last sound of the topic.