Yes, as Shade says standard creatures keep their speed when they "size up".
Still, if you're doing a template for a "supersized monster" it's easy enough to include a speed increase.
For example, we did a
conversion of the Mystaran Gargantua which doubled the base creature's speed.
Apply that template to a Wolf and you get...
Mystaran Gargantua Wolf
Gargantua Animal
Hit Dice: 16d8+144 (216 hp)
Initiative: +1
Speed: 100 ft. (20 squares)
Armor Class: 18 (-4 size, +1 Dex, +11 natural), touch 7, flat-footed 17
Base Attack/Grapple: +12/+37
Attack: Bite +22 melee (4d6+19/19-20)
Full Attack: Bite +22 melee (4d6+19/19-20)
Space/Reach: 20 ft./15 ft.
Special Attacks: Trample 3d8+19, trip, swallow whole
Special Qualities: Low-light vision, scent
Saves: Fort +19, Ref +11, Will +6
Abilities: Str 37, Dex 13, Con 29, Int 2, Wis 12, Cha 6
Skills: Hide -11, Listen +7, Move Silently +5, Spot +7, Survival +4*
Feats: Alertness, Cleave, Improved Critical (bite), Power Attack, Run, Track (B), Weapon Focus (bite)
Environment: Temperate forests
Organization: Solitary
Challenge Rating: 10
Advancement: 17-24 HD (Gargantuan); 25-48 HD (Colossal)
Level Adjustment: —
Trip (Ex): A Mystaran gargantua wolf that hits with a bite attack can attempt to trip the opponent (+25 check modifier) as a free action without making a touch attack or provoking an attack of opportunity. If the attempt fails, the opponent cannot react to trip the wolf.
Swallow Whole (Ex): A Mystaran gargantua wolf can swallow opponents up to three size smaller than itself by making a successful grapple check. Once inside, an opponent takes takes crushing damage equal to the creature's bite attack plus 8 points of acid damage from the creature's gizzard. A swallowed creature can cut its way out by using a light slashing or piercing weapon to deal 25 points of damage to the gizzard (AC 15). Once the creature exits, muscular action closes the hole; another swallowed opponent must cut its own way out. A Mystaran gargantua wolf's interior can hold 2 Medium opponents, 8 Small opponents, and 32 Tiny or smaller opponents.
Trample (Ex): Reflex half DC 31. The save DC is Strength-based.
Skills: *Wolves have a +4 racial bonus on Survival checks when tracking by scent.