It makes no sense to wait to bring the combined product line to the market. Also, if the closing is delayed, factors like stock market prices, trade wars, law suits and similar events could potentially interfere with the closing.
So why wait?
There are lots of things the two companies need to do to realize the commercial benefits of the merger. They have a lot more flexibility you do these things after the merger than they do while they remain separate companies.
Product pricing, bundling, distribution and joint sales are all limited by anti-trust laws until the merger closes.
Undoubtedly, these issues have been discussed at high management levels, but real implementation at the mid to lower levels of both companies can’t occur until the merger closes.
Although you never know from the outside how long it will take to close, the companies have a lot of incentive to close this merger in July rather than later.