There is no doubt she's craves for it, and you know it too. Being hesitant to verbalise her ultimate desire to ride a BBC is common because she has no clue that you want it desperately too.
I bet she gets wild when using those black dildos and it's safe to assume that the reason they became a part of your sex routine is because she can't reach an orgasm with your average penis.
Please be mindful that the ball is on you now. You need to find the courage and have this conversation sooner than later, because sex toys and role-playing won't satisfy a size-queen for long. Typically, after a while, she won't be able to cope with those urges, and instinctively she will seek the "real deal" to feed her deep BBC cravings.
The more you procrastinate, the biggest the risk for her to get seduced, and fuck a black dude behind your back. I've been there, got cheated and eventually dumped, and believe me you don't want this.
It's not an easy decision and it needs guts, but if you keep relying on dildos and dirty-talking naively thinking they're enough to keep her sexual needs fulfilled and your marriage safe, you're so damn wrong!
You must seize this great opportunity you have and make a favour not only to the sex-starving wife of yours, but to yourself too, by giving her the freedom and control to lead your relationship where it naturally deserves to be.
If you want my piece of advice is don't be afraid embracing your cuckold nature openly. Your cock will never grow larger, but predominantly it's likely your physique and male aura that fails giving her the "alpha male" vibes she's getting next to a dominant black man. The big-dick energy she is hinting about is commonly a feature that's beyond sex or actual dick size, yet it's what actually turns on a woman mentally and make her pussy dripping wet.