There's no estimated timetable for the hearing.
Whenever a hearing happens, Cambridge Analytica's response is likely to be familiar: it'll fight tooth and nail to assert its innocence. The company recently posted an article attempting to dismiss the "speculation and hearsay" surrounding data sharing, including its assertions that it and its data partner GSR obeyed the law when collecting and handling Facebook users' info. It's doubtful Cambridge Analytica will entertain any notion that was knowingly harvesting data without permission.
Whether or not the Committee accepts that response is another matter. Facebook is grappling with an FTC investigation precisely because much of the data supplied to Cambridge Analytica was obtained without consent, and senators could easily see the company as integral to those privacy violations.