From the amount of volume purchases of apple products nowadays, I imagine most modern apple products are going to be too abundant to become a pricey collectors item... Basically, if your thinking the word 'investment' then please... just save your own money and time...
No, & we don't know if his last iPhone. It's said he left Apple w/ 4 years of product ideas. Also I think Apple designs more than one phone at a time. It takes more than a year to go from concept to retail.