This is an extension that is expected at some point, but i-99 needs high speed interchanges built along I-80 near mileposts 160 and 178. Additionally, multiple sections of US 220 need to be upgraded between Lock Haven and Williamsport. North of Williamsport, US 15 which Google Maps says is now also i-99, is now an interstate quality highway all the way into New York State as of earlier this fall.
i-99 is a controversial highway in general. For one, the number was legislated by former Rep. Bud Shuster. The bulk of the initial routing was through his district, pork barrel spending. The extension to State College was a disaster as Shuster legislated that it be exempt from environmental testing. That didn’t work out — it turned out the road and all of the earth-moving required for it unleashed pyrite (aka fool’s gold) that contaminated the water supply. Four years and $79 million later, there was remediation in place. The money spent on this highway would have been better directed at improving the US 322 corridor – widening the Lewistown Narrows (which happened eventually) or upgrading the Boalsburg to Seven Mountains stretch which hasn’t happened.
In the future, i-99 will probably be posted along these roads and perhaps replace I-390 to Rochester.