Should I take time off from college (see details)?

I am hoping to get some good advice, possibly from someone who has done this. My situation is a bit tricky:

I am a Computer Science student going into my senior year. I am doing very well, but I am not sure if my degree is the one I want. Lately I have been regretting not going to a school with a dual computer science and engineering program; my school has no engineering programs or even a physics department.

My problem is I may want to transfer, but would have to take time off since I have missed transfer deadlines. I haven't found much on the web about this dilemma.

I also have two other questions pertaining to this:

1. Can time off be indefinite? For example, could I return to school even 10 years from now?

2. I am lacking certain perquisites engineering programs expect from transfer students, such as chemistry. What are my options in terms of fulfilling these? Will a school let me transfer and take them there... I am just not sure what to do since I already have so many credits.

I am really stuck between a rock and a hard place: do I just get my degree and teach myself engineering or do I hold off for a bit while I still have credits that can be transferred?

Thanks!