Why could increases in cockpit voice and image recording potentially raise privacy concerns?
I will answer this question with the caveat that it is asking for an opinion, and therefore your experience may vary due to different regulatory authorities. I answer this question from an Australian CASA context but note that while there are differences between CASA, EASA and FAA, they operate so similar that in many cases the courseware I teach to students to become an engineer under those systems is almost identical. Therefore, I feel like I am able to make an informed opinion on the matter even though the courseware I teach is primarily designed for a CASA context. Having said that, If your aviation regulatory authority is not based under those I have just mentioned, I have no idea. Go consult their regulations if that is the case.

I will now paraphrase from an avionics textbook on module 13 (avionics instruments other - Cockpit Voice Recorder system) under the CASA part 66 licence outcomes:

-It is an offence under the Air Navigation Act 1920 to disclose any information on a cockpit voice recorder for the purposes other than that listed in part 2A of this act. This means that unless it is directly related to the investigation of an accident it will not be made public.

-CVR recordings may not be used as evidence in any criminal or civil proceedings within Australia

-CVR recordings cannot be used as grounds for any disciplinary action by employers

-It is an offence to make public any CVR recording. Large fines apply

-Only the investigative authority in the course of investigation or court order is to disclose the recording for the express purpose that it is relevant to understanding the cause of an accident

My text goes on to mention things like if the recording is distressing then a transcript should be made and the original recording not played if it does not add anything to the investigation.

My textbook does not specifically mention video recording systems but I would say they fall under the definition in the Air Navigation Act 1920 and therefore treated the same. But this is something lawyers can fight over.

To some up then, due to the points raised above, I feel like there are no grounds to feel concerned about your privacy if there were increases in recording. This is due to the protection given for your personal data under the act. Each nation should have a similar act that protects people in a similar way. If it doesn't, I would hope your workers union could lobby for change. There are no downsides I can see to increasing recording time and increasing the use of video in the name of safety, especially where a rigid protocol of non-disclosure exists in the form of appropriate legislation. Privacy concerns can only exist in a world where you are not confident in the system providing the protections.

I will finish by adding another opinion on the subject. The only time I wouldn't recommend increasing recording is on very light airframes where space and weight is an issue. There is an ongoing trend in the last 40 years or more and more flight parameters being recorded under the regs, so it makes sense to also find new and innovative ways to record video and voice in the cockpit as well.