If you are an out-of-state investor investing in Philadelphia, I would recommend staying away from North Philly (and Kensington). There are some good areas around Temple, but it can get pretty dicey a couple blocks in the wrong direction. North Philadelphia is a totally different animal than CA. I have a vacant property in North Philly that I installed an alarm system and a couple flood lights so copper thieves don't get in.
Other problems with North Philly:
Bad School District (well Philly in general has bad School Districts)
Crime (both soft and hard)
Drugs, my friend saw a man in a suit selling "pizzas" in the middle of Broad Street. Broad Street!
I don't think your house would necessarily depreciate in North Philly, but could very well be abused to the point where it depreciates. It's the place that looks good on paper, but not so good to invest in. If you do end up investing there, I would recommend Section 8. As to your last question, I don't believe North Philly is up and coming, unless you go to the Temple area for the students.