^^
Unfortunately, the platforms on the Grove St station still have to be expanded before 10-car train operation can happen on the NWK-WTC line. Most of the money for this expansion is allocated from 2019 to 2023 in the PATH capital plan budget (see p. 23 of this
LINK), so I wouldn't expect that to happen before 2023 at the earliest:
But hopefully there'll be additional capacity before that, thanks to the signal upgrades. I went to a PATH information session on the CBTC/PTC signal upgrades on Tuesday, and asked them about their plans to run more trains per hour during rush hour once CBTC/PTC is put in place.
While they claim that using CBTC they'll be able to run up to 40 trains per hour through the tunnels (currently they run 30 trains per hour at rush hour), they told me that they plan on running about 36 trains per hour max, resulting in 20% more rush hour service. I'd take it with a grain of salt, but they even tout the 20% service increase in the CBTC information pamphlets they hand out at the info sessions.
They claim that CBTC/PTC will be in place by the end of 2018. They'll need extra railcars to run more service, but the PATH capital plan budget seems to have $41 million for this purpose allocated by 2017 (see p. 51 of the Capital Plan above).