WaffenSS Killer:All UNSC tech is currently available with the exception of the Shaw-Fujikawa TLE. We also don't know how the UNSC ships propel themselves in RealSpace. Other than that, we've got everything else:
not sure if this is what you mean by propel themselves but the big ships use fusion reactors. thats what the sun does and we havent figured out how to do it on earth yet.
MAC gun: http://www.technologyreview.com/Infotech/20164/?nlid=857&a=f
This SOB can send a 7 pound slug at 7 times the speed of sound.
the shipbound MAC guns send a several hundred pound slug (wanna say 700ish) at .4 time the speed of light. ya we understand the physics but building one is a different story.
All UNSC weapons are completely feasable. The Cyclops and MJOLNIR armor are all possible (and we already have something like a Cyclops).
maybe the cyclops but even that would require a big leap in battery/energy production technology. we dont have power suits that can run without being connected to a power source. the MJOLNIR armor is way out of our league. it does so much stuff. oh ya, and it runs off a small nuclear fusion reactor. we cant do that yet
The Spartan Laser is truly possible, but an advance in power storage systems is necessary.
so in conclusion, we are very far away from halo. id say several hundred years. oh i dont know, maybe 500ish years (you never know when a leap will come so its hard to say)
EDIT: oh ya i forgot to mention orbital MAC guns that fire a 3000 pound slug at .8 times the speed of light (i think) every 5 seconds. ya we are pretty far away from that