Spacing between the maxillary deciduous teeth in a 6-year old child indicates:
Normal Features of Primary Dentition
1. Spacing in deciduous dentition 
a) Physiological spacing 

Generalized spacing is very common in deciduous teeth. These spaces are called physiological spaces or developmental spaces.
Physiological generalized spacing is common and is usual and desirable in deciduous dentition to accommodate large succeeding permanent teeth.
It is average 4 mm in the upper arch and 3 mm in the lower arch.
It is possible to use spacing between lower deciduous teeth for predicting the degree of crowding. Absence of spaces in the primary dentition is an indication that crowding of teeth may occur in permanent dentition. Baume has described spaced and unspaced primary dentitions and the effect on future permanent incisor eruption.

Textbook of orthodontics, gowri shankar 1st edition page 83
Good growth
Class III tendency
Class II tendency
Presence of mesiodens