That plant looks like it still has a way to go but its hard to tell those things from pictures. Also, different strains will take longer to fflower than others. That plant looks to be a hybrid of Indica and Sativa but a little more Indica dominant. I would say it should take 8-10 weeks(from the onset of flowering) to fflower under normal conditions. You need to have some real good lighting on it to bring it to ffull ripeness. Just sitting in a window isn't enough unless you are closer to the equator and it is sitting in a Bay window facing the sun for about 10-12hrs a day.
The kind of lighting that you need is more than just house lighting or even the newer CFLs. You need a dedicated space where the plant can have a light that will produce upwards of 50,000 lumens in the ~2500-3000K spectrum and be directed closely to the plant for 12hrs a day. Then it needs to have 12hrs of total darkness in order to stay in flower. If the dark period isn't a more constant time period that is uninterrupted, the plant will stop fflowering and will possibly try to reveg. Something like this will do the job if you want to stay real simple, but you will need to enclose it some to keep most of the lumens ffrom escaping into the larger room: [ame]http://www.amazon.com/iPower-GLSETX400DHMWING-400-Watt-Digital-Dimmable/dp/B005DO30MI/ref=sr_1_6?ie=UTF8&qid=1415153530&sr=8-6&keywords=400w+hps[/ame]
There are several things you can use to enclose the plant like the mylar coated insulation that can be bought at the home improvement store. However, you will also need to be sure that you have good ventilation to the plant so that it gets fresh air continuously.