Improve velocity by additional team?

More work will probably be done overall, but that doesn't mean more value will be realized.

What do the people doing the work think of this change?

Is delivered value being continuously measured, and feedback from the users being gathered on each increment, or is there just a determination to meet a deadline with pre-defined requirements?

Where does this second team come from? There's always a cost of onboarding new people. They need to learn the product and the context, form as a team, and so on. On top of this, the people who are going to be doing this onboarding will likely be from the first team, so you'll also have reduced capacity in order to do the training and onboarding of the new team.

Then, once the team is onboarded, you still need to consider the dependencies. When possible, these dependencies should be eliminated. However, there may need to be coordination among the teams to identify work that may have an impact. There may also need to be effort to deconflict work.

I'd also consider what velocity measures. Velocity can't be compared across teams. Improving velocity doesn't mean much at a product or cross-team level. If you happen to be tracking velocity, you'll probably see a decrease in velocity from the first team as they onboard the members of the second team. After that, it depends on how good you are at managing dependencies and coordinating between the teams. You may want to look at measuring delivered value rather than velocity.

My management wants to increase the development of a new product

Why?

The Agile Manifesto says: “Simplicity--the art of maximizing the amount of work not done--is essential.”