In fact, they may be inside the reactor building as of now, on July 4, 2012.
TEPCO is sending all the survey robots it has in its possession - Quince No.2 and two Packbots from iRobot - probably to conduct the survey in the area of the Reactor 1 building 1st floor where the company is planning to drill holes to conduct an endoscope survey later to probe inside the Containment Vessel (like it has done in Reactor 2).
The robots will enter from the south-east corner entrance. The area has locations with radiation levels exceeding 1 sievert/hour, with the highest 4.7 sieverts/hour. That is where the steam was gushing from in between the floor and the pipe that goes through the floor to the basement. Packbot observed it in June last year. (At that time, TEPCO said it was 4 sieverts/hour, but the latest press release linked below says it was 4.7 sieverts/hour.)
In June, TEPCO's human workers entered the basement to measure the water levels and temperatures. Near the surface of the water, the radiation level was 10.3 sieverts/hour.
From TEPCO's handout for the press, July 3, 2012:
"Fukushima Daiichi Nuclear Power Station Unit 1 Reactor Building First Floor TIP Room and South Area Inspection (July 4, 2012): Scheduled Access Route for the Robot"
-Visual inspection of TIP Room (Acquire images and videos)
-Measure the dose rate, temperature, humidity and dust
density in TIP Room
-Support opening the key to TIP Room (Provide images taken
from different angles)
-Support opening the door of TIP Room (Provide images
taken from different angles)
-Open the key to TIP Room
-Open the door of TIP Room (and keep it open)
-Support the dose rate measurement in the South area
(Confirm the position of the 2nd Packbot)
-Visual inspection of the South area (Acquire images)
-Measure the dose rate in the South area (at 15cm and
150cm above the floor)
Beautiful collaboration, in the area where the highest radiation level measured was 4.7 SIEVERTS/hour. I wish them luck.