Here is what I know.
(This is from someone who has dealt with the twins several times for business, and before Reloaded came came out, and before and after they shot their parts in the movie(s).
They filmed several scenes. 1 is them in the castle chasing the Keymaker and such. Another is in the parking lot fighting Trinity and Morpheus. One is them on the highway. There are several other scenese with them that were filmed.
I have been told that one dealt with a (hope this works)
Spoiler:
subway station/train and another dealt with a dance club
Now this does not mean that they will be in the next movie, just that they "could" be in it. It basically boils dwon to what ends up on the cutting room floor and what goes into the movie.
As an aid to those who do not want to read the spoiler.
My source (and I heard this having nothing to more in general conversation before Reloaded came out) is that several scenes with the Twins were shot. We saw several Reloaded (castle, castle hallway, castle garage, freeway). Other scences/locals were shot.
These could be in the next movie.
I do not know the intamite details (like dialoge or if they said something like "to defeat Smith, you must steal his mojo"😉. Just a general description of what kind of scene was shot. Some of the descriptions sound like things I saw in the trailer.
So, the end all is there is probably footage to put them in the next movie. Then again, they could have been cut for a variety of reasons.