This is my educated guess on how the 50th birthday will be based on my experiences with past special parties like Captain EO, Star Tours Openings, 25th Birthday Party etc................
Friday July 15th - normal day 8am to Midnight
Saturday July 16th - park closes at 10pm - everyone out - reopens at 12midnight for special 50th Birthday ticket holders only! (my guess $75.00 cost, Annual Passes not included ) - park is then open straight until 2am on Monday night (Tuesday AM) 50 HOURS!!! - regular guests can enter starting at 8am on Sunday morning and stay until 2am Monday night, (if they don't leave! Only guests with an wristband can enter the park after midnight and before 8am).
Sunday July 17th - THE DAY! Regular guests can only get in starting at 8am. A special birthday ceremony in front of the castle at 10am. Free birthday cake, party hats etc. The Space Mountain Re-Opening ceremony at 12noon! Press only for 2hrs. A special extended fireworks show that night. Only guests with an wristband can enter the park after midnight and before 8am. By 12 noon Disneyland has reached capacity everyone else is sent to DCA. After 6pm guests are allowed back into Disneyland (Once in the park do not leave!)
Monday July 18th - open until 2am. Regular guests can only get in starting at 8am. Only guests with an wristband can enter the park after midnight and before 8am.
Tuesday July 19th - normal day 8am to Midnight